1. Field of the Invention
The field of art to which this invention pertains may be generally located in the class of devices relating to valves. Class 137, Fluid Handling, Subclass 318 United States Patent Office Classification, appears to be the applicable general area of art to which the subject matter similar to this invention has been classified in the past.
2. Description of the Prior Art
It is necessary in many instances to terminate the flow of fluid through a fluid flow system, such as a gas line or a liquid line, because of a failure in the fluid flow system due to a leaking valve, a crack in the fluid flow line, or other problems which require the fluid flow system to be shutdown to make the required repairs. It is also necessary in many instances, because of required maintenance or changes in a water system, a refrigeration system, an air conditioning system and other fluid flow systems to temporarily shutdown such systems for many hours. Such problems can involve the loss of many work hours, and the closing of buildings containing fluid flow systems wherein the flow of fluid therethrough must be terminated for either a short period or a long period.
Heretofore it has been proposed to provide a valve insertable in a fluid flow line which could be attached to the fluid flow line and which included a hole cutter means for cutting a hole through the fluid flow line and placing a tubular seal in the hole to block the flow of fluid downstream of the blocked hole. Such a line insertable valve is disclosed and described in U.S. Pat. No. 4,552,170 to Margrave. However, experience has shown that the Margrave line insertable valve disclosed in said patent failed in practice when it was attempted to put it in actual use. The failure of the Margrave valve shown in said patent was due to inherent structural defects which permitted fluid leakage from the porous cast metal body employed in the Margrave valve, as well as leakage through the opening in the valve body for the shaft carrying the hole cutter. Furthermore, the hole cutter employed in the Margrave valve was incapable of cutting through both walls of a fluid flow line on which said valve was mounted, due to jamming of the hole cutter by the slug removed from the first wall of the fluid flow line. The Margrave valve was incapable of sealing the hole cut through the first wall of a line because of the jamming failure of the hole cutter as well as the inefficient sealing action of the tubular seal employed in the Margrave valve.